Canada is the U.S.'s largest trading partner, and the US economy would struggle to make up for Canada's absence, Heyman noted.
G-7 leaders jumped to the defense of Trudeau and reiterated their support for their joint statement.
Navarro, for his part, suggested that he was following orders - but made a poor choice of words in doing so.
"My mission was to send a strong signal of strength".
The Trump administration took umbrage at an ally publicly criticizing US policy just before a historic meeting with Kim Jong-Un.
"Obviously we support the continuing efforts by the president on North Korea", the prime minister said.
Hayden told CNN there was no strategic value in Trump's actions and, particularly, in his administration's response.
Mr Trump said he chose to back out of the G-7 communique after watching Mr Trudeau's closing summit news conference, at which he warned that Canada would not be pushed around on tariffs - a point the Canadian prime minister had made several times before.
They said the country's leaders have been reconsidering their approach to the United States because the Trump campaign was so vocal in its criticism of the North American Free Trade Agreement, and that the issue was of concern across the Canadian political spectrum. I like him. But he shouldn't have done that.
"[Trudeau] really kind of stabbed us in the back", Kudlow said. President Trump had announced new tariffs on steel and aluminum, explaining that Canada and European nations had taken advantage of the trade process.
She said the tariffs were "a naked example of the United States putting its thumb on the scale in violation of the very rules it helped to write".
The backstabbing charge seems over the top, but the White House's contention is that Trudeau ought to have capped the G-7 summit by talking about Trump and the U.S.
While other presidents and prime ministers have had testy relations - president Richard Nixon famously used a profane word, behind closed doors, to refer to Trudeau's father Pierre Trudeau, also in the context of trade talks - neither side has demonstrated this level of animosity since John Diefenbaker feuded with John F. Kennedy in the early 1960s.
Asked if he was offering Trudeau an apology, Navarro said "yes, absolutely".
Ambrose said the government needs to consider what more it's willing to put on the NAFTA table, keeping in mind that "what's at stake is just so much bigger than our pride. So you're looking at a million jobs here in Ontario".
The EU has "a $151 billion surplus" which it should use to fund "military", said Trump Monday, referencing what Trump believes is the US' outsized financial contribution to North Atlantic Treaty Organisation. Among other things, she said the government should be preparing to keep pace with corporate tax cuts and tax breaks south of the border.
Freeland described Trump's plan to slap tariffs on Canada under the pretext of national security as ridiculous and urged the United States to invest in its worldwide alliances.